The health benefits of PA are widely accepted, aiding in reducing the risk of cardiovascular disease, diabetes, stroke, obesity, and some cancers. Recommendations are to engage in 30 minutes a day on most days of the week, however, <of adults are inactive with higher rates of inactivity among racial and ethnic minority women. The Guide to Community Preventive Service found social support interventions to be effective in increasing PA. Therefore, the proposed study seeks to examine the feasibility and efficacy of a novel "Culturally-Appropriate Peer-based Motivational Interviewing" (CAPMI) intervention that targets behavioral skills, communication and social support for increasing PA in sedentary African American (AA) women. The overarching theoretical rationale for CAPMI centers on the role of social influence in the behavior change process. Family, friends and supportive others exert influence on one's motives, preferences, behaviors, and outcomes. As such, there is a clear need to target natural networks in behavior change studies. Motivational Interviewing (MI) is an approach that may help individuals enhance the quality of support given and received from their supportive others. MI focuses on helping individuals increase motivation by reducing barriers to change and resolving ambivalence for a given behavior by using empathy, encouragement, and non- confrontational methods. This method has been used extensively in addiction studies, but is showing promise for improving other health behaviors such as diet and PA, and among minority populations. The primary goal of the proposed intervention is to examine the efficacy of using motivational interviewing techniques to foster better reciprocal social support. Specific aims are: (1) to conduct formative research using semi-structured in- depth interviews and focus groups with sedentary AA women to investigate the role and importance of social support for PA;(2) to determine the feasibility of recruiting and implementing CAPMI in sedentary AA women;and (3) to pilot test and evaluate the efficacy of the CAPMI in increasing PA, social support, self-efficacy and reducing barriers to PA at post-intervention compared to an attention control group. Women (N=80;40 dyads) recruited in natural non-intimate dyads (i.e., family members or friends) will be randomly assigned to either the CAPMI: (1) peer-based MI and behavioral skills (e.g., goal setting and problem solving) training;(2) self-help materials (e.g., workbook, training DVD and PA newsletters);(3) pedometer;or Attention Control (AC): (1) self- help materials (PA newsletter only);(2) pedometer. Prior to the start of the intervention, focus groups and paired semi-structured in-depth interviews will be conducted with AA women to examine sources of social support for PA. Intervention and control participants will be compared on minutes of self-report moderate- intensity PA, social support, and PA barriers at four time-points: baseline and Weeks 4, 8, and 12 post-baseline. We also propose a brief plan of process evaluation using the RE-AIM framework to determine reach, efficacy, and implementation of the intervention. Public Health Relevance: Non-intimate natural networks, i.e., family members/friends, can play a major role in increasing physical activity (PA) in African American women. The proposed culturally- appropriate peer-delivered MI intervention (CAPMI) is designed to address this issue by enhancing the type of motivation and support that peers provide for PA. The goal of this study is to ultimately reduce racial/ethnic disparities in cancer by developing prevention interventions that address AA women's'social resources, and to enhance our knowledge of how to move women from being sedentary to meeting PA recommendations for cancer prevention.